temp question

rfix'n · 04-17-2003, 09:17 AM

Concerned with my high temps I purchased an infrared temp sensor. My guage indicates 230F but the ? oil line going from the engine to the t-stat is reading 160F at the engine and 110F right before the t-stat. At 110F I don't think the thermostat is evening opening. The lines running up to the Carrera cooler are at 80F - 90F.

Would measuring the temp on the outside of the oil line have that much of a difference from the temp sensor? Or do I have something amiss in my guage or temp sensor?

This infrared sensor is a cool toy, I'm shooting everything is sight!

Chuck Moreland · 04-17-2003, 09:56 AM

Do you have a mismatch between sensor and guage?

Are you getting repeatable measures with that IR thermometer? My experience with IR thermometers is they aren't useful on oil lines. I think the problem is the size of the oil line is too small vs the thermometer field of vision. Perhaps some thermometers are better than others.

Better to measure the oil tank temperature since it is a much larger surface.

If the engine is only 160F, the thermostat will be closed. You can confirm this the old fashioned way - put your hand on the oil lines at the oil cooler end.

911pcars · 04-17-2003, 10:01 AM

I agree w/Chuck. Most IR temp gauges have an error factor which translates into a larger field of "vision" as the sensing distance increases. Get as close to the object as you can and it'll be more accurate. The oil tank is a good target.

Sherwood Lee
http://members.rennlist.org/911pcars

rfix'n · 04-17-2003, 10:13 AM

Thanks, I'll take a temp reading at the tank next. I'm starting to think I do have a mismatch. Might be wishful thinking but I was right next to the line at the t-stat and did put my hand on the lines next to the cooler, it was luke warm. I was probably 3 feet from the place I took the reading from the ? line next to the engine.

Bill Verburg · Bill Verburg's Garage

Try using one of those meat thermometers w/ a long probe right into the oil tank. Any external reading will be low. You want to measure the oil temp not the pipe temp. The tank reading will still be lower than the guage but it is the best you can do. There are only 2 senders used since the sixties. The change occured w/ the '78 models.

sammyg2 · 04-17-2003, 12:02 PM

Another thing about infra-red temp guns, if you are shooting something shiny like stainless steel you will get a bad reading. Best bet is to try and measure something that's black.
At work we use flat black spray paint and paint the measurement points to ensure consistancy.

rfix'n · 01:20 PM

I appreciate all of the tips guys!

I'm stumped though, I have established that I am not getting oil up to the front cooler. T-stat is new and the supply line #9 below(also new) to it only registers 100F right before the t-stat. Whats weird is that the same line when measured close to the engine registers 180F. What Bill says about the line reading low makes sense because the dash guage said 210F. Tank registered 180F.

I have two theories, although both seem improbable. 1) the ? line is blocked and oil is not getting past or to the t-stat. 2) the t-stat bypass is not working creating a blocking of oil flow to the area.

The line going back from the t-stat to the tank (#10 below) actually reads higher than the ? line (#9) going from the engine to t-stat.

I guess my next step is to take the ? line off and check it out and then take the t-stat off and examine it.

Any other suggestions?

rfix'n · 04-17-2003, 02:23 PM

Just had a really scary thought, what if it was the scavange pump? Is there any way to test this? Is this a typical symptom of the scavenge pump going out?